Telecommunications networks using large bandwidth optical fibers and optoelectronic devices can carry much more information than their electronic counterparts. Such networks use various multiplexing schemes to pack as much information as possible into the optical signals before transmission. The performance of optical networks, however, is limited by the switching and signal processing functions, which are presently performed using electronic devices. These create system bottlenecks resulting from the detection and re-radiation of optical energy, the limited bandwidths of electronic switching and processing devices, and the incoherence between the input and output light. Therefore, it is necessary that optical switching technology be developed to exploit the large bandwidth of optical fibers and meet the telecommunications demands of the future.
In general, optical switching systems are needed to switch among the total permutations of interconnections between M sources and M receivers. One approach to optical switching uses cylindrical lenses in conjunction with a spatial light modulator to fan out the optical input so that the light from each fiber of an input array is broadcast over the output array. A major shortcoming of such a system is that the energy efficiency for an array of N sources and N receivers is no better than 1/N because of the fan out of the input signals. Furthermore, if the output fibers are single mode fibers, as in long-haul telecommunications, there is an additional fan-in loss factor of 1/N resulting from mode mismatch in coupling the light signals into the single mode fibers. Thus, the theoretical efficiency becomes 1/N.sup.2, which is extremely inefficient for large N. Optical switching can also be accomplished with LiNbO.sub.3 integrated optical switches. Integrated optical switches, however, tend to have variable performance from channel to channel and are unacceptably large physically for arrays greater than 4.times.4. An additional drawback of prior optical switching devices is that each connection is realized through a unique channel that cannot be shared. As a consequence, such devices have no tolerance for defective switches in any channel. Thus, there is a need for a compact and efficient optical switch module suitable for interconnecting and switching among at least an 8.times.8 array of optical sources and receivers.